Rotary disc-type heat exchanger

ABSTRACT

A disc drier is described where internally, in each disc, a number of corresponding profiles are arranged, which, when the two disc halves are put together to one disc, establish an engagement with each other to stiffen the disc.

[0001] The present invention relates to a heat exchanger device, for heating, cooling or drying of a material, as the device comprises a stationary drum with a hollow rotor for circulation of a heating or cooling medium arranged internally in the drum, in which a number of disc-formed bodies are fitted to the rotor in order to comprise the medium in the rotor, where the disc-formed bodies are shaped in that two plate-formed halves are fastened together. More specifically, the invention relates to an arrangement and a method for assembling and securing a disc for use in such a heat exchanger.

[0002] Today, different kinds of drying apparatus are used for drying of different types of water-containing materials. However, in the last few years, so-called disc driers or have increasingly been used, especially in connection with drying of glue-containing materials that normally create problems for other conventional drying equipment. Even if a drying process is used to exemplify the invention, it must be pointed out that such discs according to the invention can be used in any heat exchanger, i.e. also for general heating and cooling of a material. Furthermore, the invention is independent of the medium that is used. Normally, steam is used for heating/drying, but it is also common to use heating oils.

[0003] The reason for such disc driers demonstrating such good properties in relation to drying of glue-containing materials is the way in which these disc driers are constructed. The characteristics of such a disc drier are that it consists of a stationary chamber, and that a rotor is arranged inside this chamber, with a number of disc-formed discs welded perpendicularly onto the central rotor tube.

[0004] The discs are placed a certain distance apart. The hot fluid medium flows through the rotor and out into the disc-formed discs, and heats these discs so that the moisture in the material in the chamber evaporates as the material comes into contact with the hot surfaces of the discs. Thus, it is a premise for attaining an effective heat exchange that the discs have a large surface.

[0005] Arranged between each two discs is a scraper bar that, to a certain extent, will prevent the glue-containing materials sticking to and getting stuck on the disc surfaces. Furthermore, small paddles are mounted on the periphery of the disc plates to promote an overall slow forward movement of the material that is to be dried.

[0006] The shaping of the disc plates themselves can vary and several types are described.

[0007] U.S. Pat. No. 3,800,865, to Stord Bartz Industries, describes a heat exchanger where a series of hollow disc-formed bodies are secured to the rotor. These discs consist of two plates stuck together with a number of staybolts (tie bars) welded in. These staybolts provide strength and keep the plates together when pressure is put on the hot fluid inside the discs.

[0008] Another variation of this construction is a disc construction described in DE 3838640, to Wulff Husum. This is comprised of one solid circular shaped plate, onto which is welded a number of vertical steel plates, onto each of which is welded a flat piece of steel so that the whole construction can be characterised as a ring armature on which the opposite plate segments are placed and welded on.

[0009] The two above mentioned constructions can be characterised in that, in the main, two plane plates are used in each individual disc, and that the elements which hold the plates together penetrate at least one of the plates, with the associated welding to keep the two disc plates together, and to make them leak proof for the hot fluid.

[0010] However, any such welding will entail a danger of leakage. In the main, the strength of such constructions is decided by calculating the area of the inscribed or circumscribed circles between each bar.

[0011] Other constructions use disc-like structures put together by curved plates as these give advantages when calculating the strength during internal pressure.

[0012] Additional constructions use pipe coils which are arranged in such a way that they form a disc surface, and such drier is, for example, described in U.S. Pat. No. 3,923,097. Here, it is the pipes that are the part subjected to the pressure, and this leads to advantages with regard to calculations and approval.

[0013] As mentioned above, these disc driers are used, to a large extent, to dry materials, which show glue characteristics. Materials of organic origin, and a number of other materials, contain compounds that under certain conditions make the individual particles in the material stick together.

[0014] A such water-containing material that shall be dewatered normally goes through three different phases in the drying process, namely 1) the wet phase, 2) the glue phase and 3) the dry phase.

[0015] In the wet phase (typically, the water content being above about 60%), the water content is so high that the effect of the glue-like materials is suppressed, and this phase is characterised in that there is little resistance to movement (rotor and discs are moved without much resistance to flow in the fluid-containing material that is to be dried). Furthermore, the heat transfer is relatively high in this phase. Thus, one can say that it is mainly the properties of water (and possibly other volatile compounds) that characterise this phase.

[0016] In the glue phase (typically, with a water content in the range 35-60%), a large part of the water is evaporated off, and the properties of the glue matter in the materials (the residual fluid) now dominate the physical properties of the material. This leads to the resistance to rotation is increasing considerably, and this must be compensated for by increased power uptake. Furthermore, the degree of heat transfer is reduced in this phase. The content of gluey or sticky materials in the fluid will, within a given range of water content, cause the material to aggregate into large lumps, with large resistance to shear forces. This aggregation also results in the available surface of the material that is to be dried being greatly reduced. As the evaporation process is mainly a surface process, this aggregation will lead to the heat transfer being reduced considerably.

[0017] Thus, the glue phase represents a large technical processing problem as the resistance to rotation is considerable and the heat transfer is low. Furthermore, the sticky material is likely to cause problems in that it can stick to the heating surfaces and form an isolating layer on these.

[0018] The third phase which the material goes through before it is sufficiently dry, is the so-called “dry phase”. In this phase the material is sufficiently dry so that the glue forces have no dominating influence on the course of the process. The material breaks up, i.e. the particle size is reduced again. Gradually, the remaining moisture starts to be capillary, the resistance to rotational movement is reduced, and the heat transfer increases, even if it is not as high as in phase 1.

[0019] In connection with construction of an improved disc drier it is important to possess detailed knowledge of the processes and the forces that are present during the different phases in such a drying process.

[0020] Because of the large forces that are present, especially in the glue phase, the apparatus is subjected to large loads and wear. Typically, such a drier will have a lifetime of about 10 years, or 60 000 hours. With a speed of rotation of 8-12 revolutions per minute, such a rotor will typically rotate 30-50×106 revolutions before replacement is required.

[0021] The material that is to be dried is fed into the drier at the one end and discharged at the other, i.e. the material moves in the longitudinal direction of the drier. This implies that the different discs process the material with different moisture content, i.e. the first discs treat “wet phase” material, while discs downstream of these treat material in the “glue phase”, while the last discs treat “dry phase” material.

[0022] The torsion forces that work on the disc halves can be imagined to arise because one disc half can have a relatively small resistance to a twisting movement, while the disc next to it, if this operates, for example, in the glue phase and thus experiences larger resistance to movement, will have a greater resistance to twisting.

[0023] Thus one can imagine two disc plates welded together, where one is subjected torsion and the other is not. Even if the weld along the periphery and the weld towards the central pipe will take up much of these stresses from the torsion forces, parts of these forces will also be transferred to the staybolts or ring armatures. At the same time, the staybolts and ring armatures have to take up tensile forces due to the pressure from the hot fluid, and tension forces in particular in the glue zone where glue particles are pressed between scraper and disc surfaces.

[0024] Therefore, the staybolts or ring armatures will be subjected to changing forces in the form of tension, stress and torsion during one rotation.

[0025] The above mentioned combination of changing tension, stress and torsion forces that these disc driers are exposed to, especially in processing of glue-containing materials, means that the welding in of the above mentioned staybolts, ring armatures, or curved plates will be very critical concerning weld cracks in a time perspective.

[0026] Any such crack in a critical area can develop to a leakage that can take a long time to fix because of the cooling time of the rotor. A large modern disc drier can have as many as 70 discs with more than 140 staybolts in each disc. Thus, with two welds in each tie bar there will be 10-15 000 spots of potential leakage.

[0027] Therefore, work to bring about a disc construction without the staybolts or ring armatures has been carried out for a long time, and an aim of the present invention is thus to provide a solution in which the two plates that make up a disc can be fastened together without the problems described above.

[0028] The present invention solves this technical problem and is characterised in that internally, on each of these corresponding disc halves, a set of corresponding profiles is arranged such that the corresponding profiles are moved mutually in relation to each other when the disc halves are placed together, to establish engagement with each other and thus stiffen the disc formed bodies. Further embodiments of the invention are described in the claims 2-11.

[0029] The present invention will now be described in detail, with reference to the enclosed figures, in which:

[0030]FIG. 1 shows in a perspective view the inside of one half of a disc and the profiles that are welded to this.

[0031] FIGS. 2A-C shows how the profiles fitted on the two disc halves establish engagement with each other during construction to stiffen the structure.

[0032] FIGS. 2D-E shows in section an embodiment of profiles.

[0033]FIG. 3 shows an alternative embodiment of the profiles where these are arranged in a circular extension on the disc half, and where the profile is such that a broken threaded anchorage point is established.

[0034]FIG. 4 shows a catch anchorage point and the cross section of the profile for this catch anchorage point is shown in FIG. 4b, which stretches in a circular extension on the disc half.

[0035]FIG. 5 shows an unbroken threaded anchorage point.

[0036]FIG. 6 shows in a cross section a disc where through bolts are fitted for further holding together of the two disc halves.

[0037]FIG. 1 shows the “inside” of a disc half 12. It can be seen in the figure that the disc half 12 is equipped with a number of profiles 14. The cross section of these profiles 14 can vary, but one embodiment of the invention has a section as shown in FIG. 2. On the two disc halves 12,12′ which together shall form a disc, the profiles are corresponding to each other, given with the reference numbers 14 and 14′ respectively. The central concept is that these profiles, when constructing the two opposite disc halves 12,12′ into one disc, are twisted and at the same time forced against each other, so that the corresponding profiles 14,14′ engage with each other. Thus, a catch anchorage point that stiffens the disc is established.

[0038] The profiles 14,14′ have a certain length, and the profiles 14,14′ are, in a preferred embodiment of the invention, arranged in their longitudinal direction in the radial direction of the disc, as shown in FIG. 1.

[0039] The profiles 14,14′ are evenly distributed over the whole disc surface and will typically number from 10 to 50 per disc half, more preferably about 25-35 per disc half.

[0040] It is an advantage to arrange the profiles 14,14′ to be as long as possible, and in one presently preferred embodiment, the length of the profiles 14,14′ are about half the extent of the disc. As shown in perspective in FIG. 2, the two disc halves 12,12′ have a flat mid-section, and the profiles 14,14′ extend over a substantial part of this flat section.

[0041] As mentioned, the cross-section of the profiles 14,14′ can vary. The main aim is that the two form a catch-like engagement point with each other as the disc halves 12,12′ are pushed towards each other. The embodiment that is shown in FIG. 2 is presently the most preferred. Here it appears that each of the profiles 14,14′ have a cross-section with a mainly L-like form. The one end edge, the foot of the L, 14 a, 14 a′, respectively, is secured to the disc halves 12, 12′. Here conventional welding or other conventional methods of securing can be used.

[0042] The other part of the L-formed profile extends in parallel with the disc surface. The end edges, 14 b, 14 b′, respectively, have a shape that correspond to the shape of the sections 14 c, 14 c′.

[0043] In addition, the profiles 14,14′ can possibly be equipped with longitudinal grooves and notches (not shown) to strengthen the catch engagement point.

[0044] The FIGS. 3-6 also show other possible ways to arrange the profiles 14, 14′. The central element of the invention is that the joining together of the two disc halves 12, 12′ is carried out by way of a set of profiles 14, 14′ arranged on the inside of the two disc halves 12, 12′, and that these profiles 14, 14′ establish an engagement with each other to stiffen the structure as the two disc halves 12, 12′ are pressed and pushed against each other.

[0045] Thus, FIG. 3 shows an arrangement where corresponding profiles are arranged circularly in relation to the disc. Furthermore, the cross-section of the profiles is so that a thread-like engagement is established. A number of such profiles are shown in FIG. 3, arranged in a number of different distances to the centre (two shown here) so that a broken thread is established. FIG. 5 shows an unbroken thread.

[0046] Furthermore, shown in FIGS. 4A and 4B is a system in which the profiles 14, 14′ establish a catch anchorage point that snaps into position as the disc halves are pressed against each other.

[0047] As mentioned, the profiles according to the present invention can be combined with other solutions for joining of the two disc halves, such as staybolts and ring armatures. A further solution, where locking bolts 20 are fed through the joined disc, is shown in FIG. 6.

[0048] Thus, when the two opposite disc halves 12, 12′ engage with each other by way of the profiles 14, 14′ (as shown in FIGS. 2C and 2E), a connection that will stiffen the disc will be established as mentioned. This implies that forces, which seem to act on the one disc half, will be transferred to the other disc half by way of the profiles. This means that the above-mentioned staybolts or ring armatures can be eliminated and thus reduce the number of weld joints.

[0049] It shall be mentioned that application of the profiles according to the invention clearly can be combined with use of staybolts and/or ring armatures if this is desirable or necessary, or as shown in FIG. 6, the concept of the invention can be combined with use of continuous locking bolts 20.

[0050] In manufacture, one must expect some inaccuracy in the distance between the two disc halves. A special method of manufacturing ensures that this distance is kept below a certain minimum so that the forces that result in the deformation, which corresponds to s_(min), lie comfortably below the yield strength of the material.

[0051] Thus, each disc can be built up as follows:

[0052] Disc half (12, 12′) preferably manufactured from one steel plate or a plate of stainless steel. Pressed and manufactured according to certain tolerances.

[0053] Internal profiles (14, 14′) preferably of steel or stainless steel. These are machined according to special tolerances so that the total inaccuracy in the manufacture of the disc can be kept at a certain level.

[0054] Dividing plate (not further shown in the figures) to collect and empty the condensate that arises inside the disc from condensing steam.

[0055] Pipe (not further shown in the figures) for steam entry into the disc.

[0056] Pipe (not further shown in the figures) for condensate discharge.

[0057] As the invention is now described with reference to some specific embodiment examples, it must be accepted that a series of different modifications is possible within the concept of the invention. The central concept is that the tensile, compressive and torsion forces that arise in such constructions, and which are described above, are partly or completely taken up by two non-through profiles that are encroached during assembly. 

1. Heat exchanger device for heating, cooling or drying of a material, with the device comprising a stationary drum with an internally arranged hollow rotor containing a heating or cooling medium, where a number of disc-formed bodies are fitted to the rotor in order to comprise medium in the rotor, where the disc formed bodies are formed in that two plate-formed disc halves (12, 12′) are stuck together, characterised in that a set of corresponding profiles (14, 14′ respectively) are internally fitted onto each of the corresponding disc halves (12, 12′ respectively) so that the corresponding profiles (14, 14′) establish an engagement with each other for stiffening of the disc-formed bodies as the disc halves (12, 12′) when being put together are mutually moved in relation to each other.
 2. Device in accordance with claim 1, characterised in that the mentioned profiles (14, 14′) have largely an L-shaped form.
 3. Device in accordance with one of the claims 1-2, characterised in that the end edges (14 b, 14 b′) of the profiles are adapted to correspond to the sections (14 c, 14 c′) of the profiles.
 4. Device in accordance with one of the claims 1-3, characterised in that the disc comprises a dividing plate to collect and empty the condensate that is formed in the disc.
 5. Device in accordance with one of the claims 1-4, characterised in that the discs comprise pipes for steam entry, and pipes to discharge condensate.
 6. Device in accordance with one of the claims 1-5, characterised in that the disc halves (12, 12′), in addition to the mentioned profiles (14, 14′), are kept together by conventional welding.
 7. Device in accordance with one of the claims 1-6, characterised in that in addition, conventional staybolts 20 and ring armatures are used to take up the tension in the disc construction.
 8. Device in accordance with one of the claims 1-7, characterised in that the profiles are arranged radially inside the disc.
 9. Device in accordance with one of the claims 1-7, characterised in that to establish engagement between the two disc halves the profiles are arranged in a axial direction.
 10. Device in accordance with claim 9, characterised in that the profiles are given a form so that a threaded anchorage point is established between the two disc halves.
 11. Device in accordance with claim characterised in that the threaded anchorage point is broken. 